The present invention relates to a filter arrangement and filtration method. More specifically, it concerns an arrangement for filtering particulate material from a gas flow stream, for example, an air stream. The invention also concerns a method for achieving the desirable removal of particulate material from such a gas flow stream.
The present invention is an on-going development of Donaldson Company Inc., of Minneapolis, Minn., the assignee of the present invention. The disclosure concerns continuing technology development related, in part, to the subjects characterized in U.S. Pat. Nos.: B2 4,720,292; Des 416,308; 5,613,992; 4,020,783; and 5,112,372. Each of the patents identified in the previous sentence is also owned by Donaldson, Inc., of Minneapolis, Minn.; and, the complete disclosure of each is incorporated herein by reference.
The invention also relates to polymer material and fiber that can be manufactured with improved environmental stability to heat, humidity, reactive materials and mechanical stress. Such materials can be used in the formation of fine fibers such as microfibers and nanofiber materials with improved stability and strength. As the size of fiber is reduced the survivability of the materials is increasingly more of a problem. Such fine fibers are useful in a variety of applications. In one application, filter structures can be prepared using this fine fiber technology. The techniques described concern structures having one or more layers of fine fibers in the filter media. The structure, composition and fiber size are selected for a combination of properties and survivability.
Gas streams often carry particulate material therein. In many instances, removal of some or all of the particulate material from a gas flow stream is essential. For example, air intake streams to engines for motorized vehicles or power generation equipment, gas streams directed to gas turbines, and air streams to various combustion furnaces, often include particulate material. The particulate material can cause substantial damage to operating equipment. The particulate is preferably removed from the gas flow upstream of the engine, turbine, furnace or other equipment.
In other instances, production gases or off gases may contain particulate material, for example, those generated by processes that included milling, chemical processing, sintering, painting, etc. Before such gases can be, or should be, directed through various downstream equipment and/or to the atmosphere, a substantial removal of particulate material from those streams is important.
The invention relates to filter elements in structures and to improved filter technology. The invention also relates to polymeric compositions with improved properties that can be used in a variety of related applications including the formation of fibers, microfibers, nanofibers, fiber webs, fibrous mats, permeable structures such as membranes, coatings or films. The polymeric materials of the invention are compositions that have physical properties that permit the polymeric material, in a variety of physical shapes or forms, to have resistance to the degradative effects of humidity, heat, air flow, chemicals and mechanical stress or impact in filtration structures and methods.
In making non-woven fine fiber filter media, a variety of materials have been used including fiberglass, metal, ceramics and a wide range of polymeric compositions. A variety of techniques have been used for the manufacture of small diameter micro- and nanofibers. One method involves passing the material through a fine capillary or opening either as a melted material or in a solution that is subsequently evaporated. Fibers can also be formed by using xe2x80x9cspinneretsxe2x80x9d typical for the manufacture of synthetic fiber such as nylon. Electrostatic spinning is also known. Such techniques involve the use of a hypodermic needle, nozzle, capillary or movable emitter. These structures provide liquid solutions of the polymer that are then attracted to a collection zone by a high voltage electrostatic field. As the materials are pulled from the emitter and accelerate through the electrostatic zone, the fiber becomes very thin and can be formed in a fiber structure by solvent evaporation.
As more demanding applications are envisioned for filtration media, significantly improved materials are required to withstand the rigors of high temperature 100xc2x0 F. to 250xc2x0 F. and up to 300xc2x0 F., high humidity 10% to 90% up to 100% RH, high flow rates of both gas and liquid, and filtering micron and submicron particulates (ranging from about 0.01 to over 10 microns) and removing both abrasive and non-abrasive and reactive and non-reactive particulate from the fluid stream.
Accordingly, a substantial need exists for polymeric materials, micro- and nanofiber materials and filter structures that provide improved properties for filtering streams with higher temperatures, higher humidities, high flow rates and said micron and submicron particulate materials.
Herein, general techniques for the design and application of air cleaner arrangements are provided. The techniques include preferred filter element design, as well as the preferred methods of application and filtering.
In general, the preferred applications concern utilization, within an air filter, of barrier media, typically pleated media, and fine fibers, to advantage.
The filter media includes at least a micro- or nanofiber web layer in combination with a substrate material in a mechanically stable filter structure. These layers together provide excellent filtering, high particle capture, efficiency at minimum flow restriction when a fluid such as a gas or liquid passes through the filter media. The substrate can be positioned in the fluid stream upstream, downstream or in an internal layer. A variety of industries have directed substantial attention in recent years to the use of filtration media for filtration, i.e. the removal of unwanted particles from a fluid such as gas or, in certain instances, liquid. The common filtration process removes particulate from fluids including an air stream or other gaseous stream or from a liquid stream such as a hydraulic fluid, lubricant oil, fuel, water stream or other fluids. Such filtration processes require the mechanical strength, chemical and physical stability of the microfiber and the substrate materials. The filter media can be exposed to a broad range of temperature conditions, humidity, mechanical vibration and shock and both reactive and non-reactive, abrasive or non-abrasive particulates entrained in the fluid flow. Further, the filtration media often require the self-cleaning ability of exposing the filter media to a reverse pressure pulse (a short reversal of fluid flow to remove surface coating of particulate) or other cleaning mechanism that can remove entrained particulate from the surface of the filter media. Such reverse cleaning can result in substantially improved (i.e.) reduced pressure drop after the pulse cleaning. Particle capture efficiency typically is not improved after pulse cleaning, however pulse cleaning will reduce pressure drop, saving energy for filtration operation. Such filters can often be removed for service and cleaned in aqueous or non-aqueous cleaning compositions. Such media are often manufactured by spinning fine fiber and then forming a layer, a web or an interlocking web of microfiber on a porous substrate. In the spinning process the fiber can form physical bonds between fibers to interlock or integrate the layer and to secure the fiber mat into a layer. Such a material can then be bonded to a substrate, and fabricated into the desired filter format such as cartridges, flat disks, canisters, panels, bags and pouches. Within such structures, the media can be substantially pleated, rolled or otherwise positioned on support structures. The filter arrangements described herein can be utilized in a wide variety of applications including: equipment enclosures, vehicle cabin ventilation, cabin air filters, on-road and off-road engines; and, industrial equipment, such as compressors and other related applications.